Rationale for Ada 2012
9.3.9 In out parameters for functions
The proposal was to allow functions to have parameters
of all modes. The rationale for the proposal was well summarized thus
"Ada functions can have arbitrary side effects, but are not allowed
to announce that in their specifications".
But strangely, this AI was abandoned quite early
in the Ada 2005 revision process on the grounds that it was "too
late". (Perhaps too late in this context meant 25 years too late.)
However, in Ada 2012, the bullet has been bitten
and functions can indeed now have parameters of all modes. See the discussion
in Section
4.2 of the chapter on Structure
and Visibility.
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